Two of those arrows (upper left and lower right) are pointing to what looks like 500 volt silver mica caps. It appears to me that those caps are already "replacement caps" because the original Dynaco PAS preamp boards did not come with silver mica capacitors. Silver mica capacitors are nearly always dead stable.

You should replace those "black cat" capacitors. These are the original caps that the board came with and are probably 40 + years old.

looking at the schematic answers your questions, the 7500pf caps (6800pf replacements work fine) are part of the bass controls, so aren't needed if the tone controls are bypassed, all of the caps in the photo are marked as 400vdc